This Invention relates to the field of firearms and provisions for modifying automatic firearms for training purposes. In particular, it relates to automatic gas-operated weapons adapted to fire reduced-energy ammunition in a blow-back mode and to training ammunition for use therein.
Reduced-Energy Ammunition for Training Purposes
In military and police firearms applications almost all of the ammunition consumed is used for training. For some training purposes, however, standard (service) ammunition is inappropriate. An alternative type of training ammunition, represented by U.S. Pat. No. 5,359,937 (adopted herein by reference) fires a low-mass projectile relying on a telescopically-expanding, reduced-energy cartridge designed to provide blow-back cycling of suitable modified, recoil-operated or gas-operated automatic weapons.
Advantages of the reduced-energy ammunition are that it has a shorter range and lower penetration capacity than standard ammunition. This permits the use of smaller, less secure firing ranges, even improvised ranges, as training facilities. However, if standard ammunition were accidentally employed in such facilities, unexpected dangers would arise from its increased striking power and range.
Appropriate modifications to certain semi-automatic and automatic weapons allow normal weapon functioning, including recoil, through a pure blow-back action when firing such training ammunition. Such a system, when firing low mass marking cartridges, for example, allows effective close-range, force-on-force training. Tactical scenarios that can be effectively simulated include counter-terrorism, close quarters combat, trench clearing, fighting in wooded areas, urban fighting, room clearing, dynamic entries, and protection of dignitaries.
Confidence is gained because the training ammunition/conversion kit system allows the trainees to use their own service weapons during stressful exercises that involve shooting and being shot at under realistic tactical situations. The training is safe when properly conducted, but there is a pain penalty for participants who are hit. It is the fear of this penalty that encourages the participants to treat the training scenarios as xe2x80x9cthe real thingxe2x80x9d and to behave as though their lives were at risk.
Modification to Weapon to Permit Firing of Reduced-Energy Ammunition
When firing standard ammunition with its abundant associated energy, it is necessary in many weapons to lock the barrel to the slide (for pistols) or to the bolt/bolt carrier assembly (for gas-operated rifles or machineguns) during the beginning of the firing action for a period long enough for the bullet to exit the barrel muzzle while the breech is still closed. This allows the chamber pressure to drop before the breech opens to extract and eject the spent cartridge case. A locking mechanism couples the barrel to the slide or bolt/bolt carrier assembly for the first portion of the discharge, and then releases the slide or bolt/bolt carrier assembly, usually with the aid of a cam. Upon unlocking, the slide or bolt/bolt carrier assembly continues its rearward travel until, after the spent cartridge case has been ejected, it returns under the influence of the recoil spring to receive and chamber the next round from the magazine en route to its in-battery position.
In a training system such as described above there is not enough energy in the reduced-energy cartridges to precipitate sufficient recoil to unlock the barrel from the slide or bolt/bolt carrier assembly in their standard configurations. It is necessary, therefore, to omit the barrel locking mechanism and, by so doing, the recoil action becomes blow-back of the slide or bolt/bolt carrier assembly only.
The modifications to a semi-automatic pistol, for example, to permit normal functioning when firing reduced-energy ammunition as represented by U.S. Pat. No. 5,359,937 generally include replacing or modifying the barrel and sometimes replacing or adding one or two other components, depending on the weapon involved. In a gas-operated weapon, the bolt is prevented from rotating so that it will not engage the cam in the barrel extension. In both instances, the modifications result in a pure blow-back action of the weapon upon firing reduced energy ammunition which is sufficient to cycle the weapon in a normal fashion.
Problem of Feeding in Automatic Weapons
In some instances the external configuration of the reduced-energy ammunition is not identical to that of the equivalent standard ammunition. This is the case with 5.56 mm reduced-energy ammunition as represented by U.S. Pat. No. 5,359,937, which may be shorter and have a different weight than the standard 5.56 mm cartridge, as well as having a head end of smaller diameter.
In weapons such as, for example, the 5.56 mm Fabrique Nationale (FN) xe2x80x9cMinimixe2x80x9d machinegun or the similar 5.56 mm US M249 Light Support Weapon, linked ammunition is fed into the chamber via a feed tray followed by a feed ramp. Should shorter than normal ammunition, such as the above training ammunition, be fed into the normal feed tray and said feed ramp, chambering of the ammunition may not proceed smoothly. There is the possibility of one or more cartridges skewing in the normal tray or ramp, both of which are too large to ensure the proper feeding of said ammunition.
This is important in training systems utilizing reduced-energy ammunition because the training projectile is often more fragile that the standard one. If the feeding is not true and the cartridge skews slightly prior to entering the chamber, the tip of the projectile is not strong enough to resist being damaged with the result that the weapon may jam. A first objective of the present invention is, therefore, to provide a solution to this problem by allowing the feeding and chambering of reduced-energy ammunition to proceed normally during full automatic firing of a machinegun such as the M249.
Problem of Live-Fire Exclusion
The conversion of 9 mm pistols to allow them to function normally when firing reduced-energy ammunition generally involves replacing the standard barrel by a training barrel. To ensure that a live service cartridge cannot be chambered in a converted weapon, the caliber of the training projectile and the training barrel are intentionally made smaller than 9 mm. Hence, a live round cannot chamber properly in a weapon converted for training because its projectile is too big to fit into the bore of the training barrel, and the weapon would jam.
The same approach could be taken for 5.56 mm gas-operated semi-automatic rifles and fully automatic machineguns by changing the barrel in the upper receiver barrel assembly and altering the bolt in the bolt carrier assembly to remove the locking mechanism. While such a design would ensure the exclusion of live service ammunition from being fired from a converted weapon, it would also be costly to implement and awkward for the user due to the excessive number of weapon components involved.
An alternative approach is to modify only the bolt/bolt carrier assembly, leaving untouched the upper receiver barrel assembly and the lower receiver buttstock assembly. In this way, the weapon can be rapidly and conveniently converted to fire reduced-energy training ammunition by simply exchanging the service bolt/bolt carrier assembly for a training bolt/bolt carrier assembly. This means, however, that live service ammunition would not be excluded from chambering in the standard 5.56 mm barrel. The possibility that a standard round can be fired from a converted weapon is not acceptable from a safety point of view.
It is, therefore, a second objective of the invention to provide a solution to this safety problem by preventing a live 5.56 mm cartridge from reaching the chamber of the standard barrel in the upper receiver barrel assembly of a machinegun such as the M249. By so doing, safe firing of training ammunition training in a converted weapon of this type can be conducted while positively excluding the firing of a live round of service ammunition should one (or more) be inadvertently inserted into the links feeding the weapon during training or practice sessions
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principal of the invention and the manner of its implementation. The invention in its broadest and more specific forms will be further described and defined in each of the individual claims that conclude the specification.
The invention is preferably directed to gas-operated automatic machineguns, as typified by the M249 Light Support Weapon, that are adapted to fire reduced-training ammunition as represented by U.S. Pat. No. 5,359,937.
According to one aspect of the invention a feed tray for supplying belt ammunition cartridges to an automatic firearm is provided that comprises:
(a) a tray support surface
(b) forward and rearward ammunition containment side walls mounted along opposite sides of said tray support surface
(c) a loading port orifice at the end of the forward containment wall through which cartridges may be advanced
(d) a feed lip positioned above the loading port orifice along the forward containment wall, outwardly from the tray support surface
whereby ammunition being fed through such tray and outwardly through the loading port orifice is guided in its advancement through said orifice by the feed lip. Optionally, the feed lip may be carried by an insert that is coupled to the feed tray, as by attachment to the forward ammunition containment side wall.
According to another aspect of the invention a feed tray for supplying belt ammunition cartridges to an automatic firearm is provided that comprises:
(a) a tray support surface
(b) forward and rearward ammunition containment side walls mounted along opposite sides of said tray support surface- and
(c) a training cartridge guide surface located along the inner side of the forward containment wall to reduce the distance between said containment walls to substantially the length of training ammunition cartridges to be passed through said tray for firing, which cartridges are shorter that standard ammunition in their length.
This training cartridge guide surface may be provided by a thickened forward ammunition containment wall as an integral part of such wall; or it may be provided by an insert coupled to such wall, as by fasteners, welding or an interfitting shape that allows the insert to engage with such wall.
As an example of an interfitting shape the insert may include a wall portion with a groove positioned and dimensioned to receive and interfit with the upper edge of the forward containment wall to fix the insert in place on the feed tray.
Optionally, such insert may carry the feed lip for positioning above the loading port orifice along the forward containment wall, outwardly from the tray support surface, whereby ammunition being fed through such tray and outwardly through the loading port orifice will be guided in its advancement through said orifice by the feed lip.
The foregoing summarizes the principal features of the invention and some of its optional aspects. The invention may be further understood by the description of the preferred embodiments, in conjunction with the drawings, which now follow.